Modules for converting solar energy into useful forms of energy such as heat and electricity have been in existence for many years. Because of the sun's low energy intensity and the moderate conversion efficiency of solar modules, a large array of solar modules is often required to service the end-use of the energy. Array areas from several dozen square feet to several thousand square feet are common. A thermal solar module may consist of a glazing surface and an absorber below the glazing surface. A perimeter frame is usually used to fix the glazing surface and absorber in relation to one another and to serve as a structural element for the thermal module. Moreover, the variety of surfaces on which the modules may be mounted requires a wide range of flexibility and adaptability in the methods of interconnecting the solar modules to form an array.
Another example of a solar module is a solar photovoltaic (PV) module, which consists of a series of PV cells connected in a series and parallel combination to yield a specific current and voltage output. Due to the fragility of the cells and the harsh environmental conditions they are often exposed to, the assembly of cells is often encapsulated into a rigid laminate. Most PV laminates are fabricated from a glass cover, an active layer containing the PV cells, and a back cover. While PV laminates can be directly attached to a mounting structure, it is more common for them to be framed before mounting. PV laminate frames typically consist of aluminum extrusions with an upper cavity that receives the laminate when assembled. The frame serves the purpose of increasing the rigidity of the laminate and to protect the fragile glass edge of the laminate from cracking. Frames for PV modules often include a lower flange with pre-drilled holes for affixing them to mounting structures.
Because PV modules must be electrically interconnected, they are often mounted in strings where the modules are assembled end to end to form a row of modules. Due to the fact that most mounting surfaces such as roofs are square or rectangular in nature, most PV module installations consist of multiple rows assembled in close proximity to match the general footprint of the surface on which they are mounted. Such arrangements of multiple rows of modules are generally referred to as an array.
Solar PV modules are typically constructed of a simple metal frame surrounding the PV laminate sheet that encapsulates the active solar cells. The electrical connections representing the positive and negative module outputs are often provided in the form of quick disconnect connections such as those manufactured by Multi-Contact of Santa Rosa Calif. These quick-disconnect fittings are usually provided on the ends of lead wires 2-4′ in length to allow two adjacent PV modules to be connected together.
The assembly of loose connections results in wasted time during the assembly of the solar PV modules into a larger array as the fittings must be found, connected, and any slack in the lead wires must be coiled and secured to prevent possible abrasion and shorting against the underlying mounting surface. Additionally, to prevent the quick-connects from coming undone in the field, some variants employ locking features at additional cost and complexity of installation.
In addition to connecting the voltage outputs of each solar PV module, most some electrical codes require that the module frames themselves be electrically grounded. This is often achieved by fixing a bare copper conductor to each module frame by means of a screw and washer. The grounding of module frames can be as time consuming as the wiring of the voltage outputs.
When installing the modules outlined above into a racking system, a specific order of assembly is often performed. When installing multiple modules, one often places the new solar PV module on the rack a few feet from the previously installed solar PV module. Then one must step between the two modules and reach underneath the previously installed module to acquire the free lead wire from the back of the module and then reach underneath the new module and acquire the wire of the desired polarity from the back of the new module and connect these two wires. The connectors are usually of the quick-disconnect type described above and require two free hands to connect, which can be problematic if a spare hand is necessary to hold tooling or an unsecured module on a sloped roof. The loose wire on both modules should be neatly coiled up and tied with twist ties or zip ties. The wires also should be prevented from touching or resting on the roof. Over time, wind will brush the wires across the roof surface and abrade the insulation causing exposure of the conductor and possible shorting.
Keeping to some electrical codes, all modules must be grounded to an acceptable ground source. Therefore the new module must be grounded to the entire array by connecting it to a separate bare grounding wire that is running through the array. The grounding wire would be attached to the previously installed module and the loose end must be brought close to the mounting position on the new module. A wire clamp must be attached to the frame of the new module with a screw. Then the wire must be looped through the wire clamp on the new module and then fastened into the clamp.
In the last step, one must step away from the gap between the two modules and the new module is pushed up against the previous module and mounted to the racking structure.